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INTRODUCTION
Benefits of marine reserves for conservation and fisheries management are predicated upon reduced mortality for target organisms inside reserves. Interestingly however, very few studies describe how reserves influence mortality rates (but see Attwood 2003; Willis & Millar 2005; Götz et al. 2008; Taylor & McIlwain 2010). Empirical studies of marine reserves focus on differences in organism density, abundance and size inside versus outside reserves (reviews by Côté et al. 2001; Halpern 2003; Lester et al. 2009), which is sensible because a common objective of conservation is to increase these attributes for depleted populations. Understanding changes in mortality across space in relation to reserve protection is a critical component of evaluating not only the conservation benefit of reserves, but also the contribution of reserves to fisheries management objectives.
Two important fisheries benefits of marine reserves are enhanced by understanding how reserves affect mortality rates of harvested species. The first is the use of populations inside reserves as references for unfished populations (McGilliard et al. 2010; Wilson et al. 2010; Babcock & MacCall 2011) or for estimating life history parameters used in fishery assessments (Bohnsack 1999; MacPherson et al. 2000; Taylor & McIlwain 2010; Wilson 2011). A key example of the latter involves estimates of natural mortality (M), which is an essential parameter for many fisheries models (Hilborn & Walters 1992), but is difficult to measure, in part because it is confounded by fishing activity in harvested areas outside reserves (Willis & Millar 2005). The second benefit relates to potential increases in fishery yield due to larval export, which results from increased lifetime egg production (LEP) of older, larger and more abundant organisms inside reserves, and the subsequent redistribution of this reproductive output to nearby fished areas (Botsford et al. 2009). Estimation of reserve-based increases in LEP and fisheries yield is typically based upon individual or population level models that employ estimates of natural and fishing mortality (Beverton & Holt 1957; Guénette et al. 1998). Consequently, a spatially explicit understanding of how reserves influence mortality is fundamental to understanding if and how reserves can influence LEP and fishery yield.
An additional mechanism by which reserves can benefit fisheries is the...